Some existing spreadsheet applications support only two data types: strings and numbers. Although a number can be formatted with a particular format, e.g., date, time, currency, etc., such a formatted number is still internally represented as a number and in many cases not disambiguated from other number formats. As a consequence, it is possible to perform various operations defined for the numbers data type with respect to formatted numbers, which often yield unexpected and/or nonsensical results.
For example, in some existing spreadsheet applications, numbers formatted as dates are internally represented as a fractional number of days since a prescribed epochal date (e.g., January 0, 1900), and a computation such as “January 5, 1900*January 6, 1900” results in a value of 30 since the dates “January 5, 1900” and “January 6, 1900” are internally represented as 5 and 6, respectively. Similarly, in some existing spreadsheet applications, durations are represented as a time with respect to a prescribed epochal date. In such cases, for example, a duration of 12 hours and 15 minutes is represented as “January 0, 1900 12:15 p.m.”, and a computation such as “12:15*2” results in a value of “January 1, 1900 00:30 a.m.”. Moreover, when a duration is less than 24 hours long, it is interpreted as a fraction of a single day. In such cases, for example, a computation such as “12:00*6:00” results in a value of 0.125 since the durations 12:00 and 6:00 are internally represented as 0.5 and 0.25, respectively. Furthermore, some existing spreadsheet applications execute mixed unit computations for some number formats without taking all of the units specified in a computation into consideration while still outputting a unit-based result. In some such cases, for example, a computation such as “$1+1” results in a value of $2, and a computation such as “£1+1” results in a value of £2. Thus, in many cases, existing spreadsheet applications provide incorrect, counterintuitive, and/or meaningless results when operations are performed with respect to formatted values.
Some other existing spreadsheet applications do not allow any computations between numbers that are formatted differently and/or have dissimilar units. In such cases, for example, a computation such as “$2.00+5” results in an error since the 5 does not have the same unit as the 2.